Alzheimer's disease or Alzheimer's-type dementia is a progressive degeneration of brain tissue that primarily strikes people over age 65. It is the most common cause of dementia and is marked by a devastating mental decline. Intellectual functions such as memory, comprehension and speech deteriorate.

Memory and Language Centers

Attention tends to stray, simple calculations become impossible and ordinary daily activities grow increasingly difficult, with bewilderment and frustration. These symptoms tend to worsen at night. Dramatic mood swings occur -- outbursts of anger, bouts of fearfulness, and periods of deep apathy. The sufferer, increasingly disoriented, may wander off and become lost. Physical problems, such as an odd gait or a loss of coordination, gradually develop. Eventually, the patient may become physically helpless, incontinent and unable to communicate.

Alzheimer's disease can run its course from insidious onset to death in just a few years, or it may play out over a period of as long as 20 years. More often, however, people suffer with Alzheimer's disease about nine years. It is the sixth leading cause of death in the United States. One person out of eight age 65 and over has the disease. Women are more susceptible than men and half of all nursing home residents suffer from Alzheimer's or related disorders.

What Causes Alzheimer's Disease?

Although typically people develop Alzheimer's disease as they grow older, the disease is not a natural result of aging. It is an abnormal condition whose causes continue to be investigated.

Alzheimers-Brain-Cells

The gradual loss of brain function that characterizes Alzheimer's disease seems to be due to two main forms of nerve damage:

Nerve cells develop tangles (neurofibrillary tangles)
Protein deposits known as plaques build up in the brain (Figure 2).

Researchers are not yet sure why or how these processes occur, but some of the most promising recent research points to a normally occurring blood protein called ApoE (for apolipoprotein E), which is required for the transport of fatty substances in the body.

As with all proteins, the form of ApoE that each person has in their body is genetically determined, and several different types have been identified -- some of them apparently associated with a higher risk of Alzheimer's. It may be that certain forms of ApoE lead to the nerve damage.

Another possibility is that the protein, perhaps working in combination with other substances, is involved in the formation of the plaques. Whether or not ApoE partly causes Alzheimer's disease, genes almost certainly play a role in the disease and a person with a parent who had Alzheimer's disease is at higher risk.

Other causes have been proposed. One theory suggests that ingesting tiny particles of aluminum -- from cookware, for example -- may lead to Alzheimer's. Another proposes a link between plaque formation and free radicals -- unstable, free-ranging molecules that can produce destructive chemical reactions. Both theories are controversial and unproven. Indeed, many researchers now consider the link between Alzheimer's and aluminum extremely questionable.

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